Engine liquid fuel controller



June 20, 1961 c, REGGIQ 2,988,881

ENGINE LIQUID FUEL CONTROLLER Original Filed Feb. 3, 1939 2 Sheets-Sheet 1 June 20, 1961 ENGINE Original Filed Feb. 5, 1939 F. C. REGGIO LIQUID FUEL CONTROLLER 2 Sheets-Sheet 2 United States Patent Claims. (Cl. 60-3928) This invention relates to fuel control systems and more particularly to liquid fuel metering or regulating devices for thermal powerplants, this application being a division of my application Serial No. 496,296 filed July 27, 1943, now abandoned, which is a continuation of my application Serial No. 254,355 filed February 3, 1939, and now abandoned.

The invention is of particular significance in connection with proulsion powerplants for aircraft or other vehicles, which present complex control problems due to the wide range of variations in operating conditions to which they are subject, such as ambient atmospheric conditions, speed and load.

An object of the invention is to provide a regulating device for automatically varying the rate of fuel flow to a power-plant in response to changes in a combination of various operating conditions.

Another object is to provide a regulating device for combustion powerplants which automatically varies the rate of liquid fuel flow to secure optimum ratio between fuel flow and air flow under varying operating conditions of altitude, speed and load.

The above and other objects of the invention will be apparent as the description proceeds; and while I have illustrated and described the preferred embodiment of the invention as it now appears to me, it will be understood that such changes may be made as fall within the scope of the appended claims.

In the drawings, FIGURE 1 is a sectional elevation of a fuel control system according to the invention, and FIG- URE 2 indicates a partial modification of the same. FIG- URE 3 shows an injection unit or nozzle through which fuel is sprayed into the combustion chamber, and FIG- URE 4 shows a compressor connected with the engine air induction system.

As indicated in FIGURE 1, a fuel pump 48 is connected by a low-pressure line 51 to receive liquid fuel from a tank, not shown, and discharges pressure fuel into a fuel conduit or manifold leading to injection units or nozzles as indicated at 70 in FIGURE 3 through which fuel is sprayed into the combustion chamber 60 or other suitable portion of the powerplant at a rate which varies with the fuel pressure. Such injection units or nozzles are no part of the present invention. One form thereof is described in my said application Serial No. 496,296. Another suitable type, well known in the art, consists essentially of a calibrated orifice through which a spray of fuel is discharged into the air stream or other place of utilization of the engine.

The discharge and inlet ports of the fuel pump 48 are connected through a by-pass conduit 40 controlled by a valve having a slidable element 72 biased toward closed position by a highly resilient spring 73 and actuated by means of a bell-crank lever 74. The purpose of the spring 73, as more fully described in said applications Serial No. 496,296 and Serial No. 254,355, is to apply a substantially constant bias to the by-pass valve 72 corresponding to a predetermined minimum possible value of the fuel pressure in the conduit 45. The capacity of the pump 48 is substantially larger than the maximum fuel requirements of the powerplant, hence excess fuel is constantly flowing through the by-pass, and the fuel pressure in the ,manifold 45 may be controlled at will by variably posi- 2 tioning the valve 72. The pump 48 may usual, from the engine or powerplant.

The powerplant is provided with an air induction system which may include an air compressor or blower, shown at 61 in FIGURE 4, supplying air for combustion to an air induction system or manifold 62 leading to one or more cylinders and combustion chambers. A regulator housing 88 communicates through a large duct 81 with the powerplant air induction system 62 and contains air at compressor discharge pressure and temperature. An evacuated resilient bellows 82 in said housing (for instance as shown in FIGURE 2) acts on a lever 83 to operate a pilot valve 94 having lands 84 and 85 which control admission of oil under pressure, through lines 87 and 88 connected to a high pressure system, to either side of piston 86, while a low-pressure line 89 is arranged to drain oil back to the sump. A floating or follow-up lever 90 is connected at its ends with the pilot valve and with the stem of piston 86, respectively, and at an intermediate point with a rod 91 connected through a variable-ratio lever mechanism 92 and a rod 93 with the bell-crank lever 74 which controls the fuel regulating valve 72.

The regulator housing 80 may include a temperature compensating component, indicated generally at 95, which is no part of the invention claimed herein. Such a component is described and illustrated fully in my co-pending application Serial No. 496,296.

The lower end of the rod 93 is provided (like the upper end thereof) with a roller and engages the horizontal arm of the bell-crank lever 74. A lever 79, which may be variably positioned from a manual control lever 78, has an upper arm which is connected with the lower end of the rod 93 and is arranged to vary the effective distance thereof from the fulcrum of lever 74 so as to alter the effective ratio of the bell-crank lever. The device operates as follows: the evacuated resilient bellows 82 (as shown for instance in FIGURE 2) exerts on the pilot valve 94 an upward load which is porportional to the induction air pressure. In normal operation the pilot valve 94 is maintained in equilibrium in its neutral position by a downward load of equal magnitude exerted thereon through the various elements 90-93 and 74 by the fuel pressure applied to the inner end of the regulator valve 72. Thus, for a given adjustment of levers 98 and 79, the air induction pressure or compressor discharge pressure surrounding the bellows 82 (which is a measure of powerplant air flow) and the fuel pressure in the fuel manifold 45 (which is a measure of powerplant fuel flow) are proportional. Thus, if the pressure of the air in the induction system and in the passage 81 connected therewith decreases, due for example to climbing of the aircraft to higher altitude, the bellows 82 expands and the pilot valve 94 moves downward, draining pressure oil from the lower chamber of cylinder 86 and admitting pressure oil to the upper chamber thereof. As a result, the power piston 86 moves downward causing, through elements 90-93, counterclockwise rotation of the bell-crank lever 74 and outward motion of the valve 72 to increase the flow of bypassed fuel. Hence the rate of powerplant fuel flow decreases, together with the pressure of the fuel in the manifold 45, thus decreasing the load exerted by said fuel upon the inner end of the valve 72 and in turn the magnitude of the downward load transmitted from the valve 72 to the pilot valve 94 in proportion to the decrease of induction air pressure, whereupon the pilot valve 94 returns to neutral position and stops the servo-piston 86. Con versely, an increase of induction air pressure, due for example to descent of the aircraft to lower altitude, causes the same device to increase the rate of fuel flow to the powerplant (and the fuel pressure in the manifold 45) in the desired relation to increasing powerplant air flow,

be driven, as

It will be appreciated that the arrangement described above (where the bellows 82 is a simple evacuated bellows as indicated at FIGURE 2 and contains no other compensating bellows) operates to vary the fuel pressure in the manifold 45 in direct proportion to the induction air pressure, or air compressor discharge pressure, thereby automatically securing a direct relationship between engine air fiow and fuel flow. It will also be noted that the operating connection between the air pressure sensing bellows 82 and the fuel control valve 72 does not consist merely of a system of mechanical linkages. Such a system would be lacking in accuracy inasmuch as the geometrical configuration thereof would be subject to changes upon variations in the setting of the valve 72, and the operation thereof would be impaired by frictional hysteresis. Instead, according to the invention the fuel control valve 72 is actuated from the fuel regulator 80 by means of a variable-pressure hydraulic control device consisting essentially of the variable-pressure cylinder chamber 186 situated below the piston 86. The hydraulic fluid in this chamber, often referred to as variable control oil or VCO, is constantly under pressure and exerts through the piston 86 an upward load to the end 186' of the follow-up lever 90. During steady engine operation this follow-up lever '98 is in equilibrium under said upward load (proportional to the pressure of the variable control oil in chamber 186) applied to the end 186 of the lever, a second upward load (proportional to induction air pressure) applied at the opposite end 194 through the pilot valve 94 from the evacuated bellows 82, and a downward load (proportional to the fuel pressure in the manifold 45) applied to an intermediate point 191 of the follow-up lever from the valve 72. It is therefore clear that if the air pressure surrounding the bellows 82 varies, the pilot valve 94 is caused to move so as to determine a proportional change in the variable control oil pressure, and this in turn actuates the fuel control valve 72 which by-passes a part of the fuel discharge from the constant-displacement fuel pump 48 to determine a proportional variation of the fuel pressure in the manifold 45. That is to say, an increase of the variable control oil pressure in the chamber 186 increases the fuel pressure to the nozzles by reducing the by-pass flow past the orifice 71 which is carried back to the inlet 51 of the pump 48 through the passage 48. Conversely, a decrease of variable control oil pressure decreases the fuel pressure to the nozzles by increasing the by-pass flow.

While the arrangement described above operates to vary the fuel pressure in direct proportion to the induction air pressure, such relationship between fuel flow and air flow may be altered for instance by providing a comparatively small bellows 101 located within the bellows 82 and vented to atmospheric or surrounding pressure (or substantially to engine exhaust pressure) through a passage 101' formed in the wall of the housing 80. The bellows 101 is placed above the lever 83 and is connected therewith and with the bellows 82 so as to lower or raise the pilot valve 94 upon increase or decrease of atmospheric pressure, respectively, the result being that for a given value of the induction air pressure or compressor discharge pressure surrounding-the bellows 82 the rate of fuel flow will increase with the altitude. Such an arrangement may be used to offset in part the power loss encountered in combustion engines when operating at high altitude. In particular, a single evacuated bellows 82 as shown in FIGURE 2 will be responsive to the absolute pressure by which it is surrounded. On the other hand, the bellows 82 as indicated in section at FIGURE 1 containing an inner bellows 101 vented to atmospheric pressure and with the interspace 182 evacuated will be responsive in part to the absolute induction air pressure or compressor discharge pressure, and in part to the difference between said pressure and the atmospheric air pressure.

As already stated, the lever 79, actuated by the control member 78, operates to alter the effective ratio of the bell-crank lever 74, thereby varying the fuel-air ratio. Hence the invention makes it possible so to design the regulating mechanism that a preselected fuel-air ratio is obtained for any given position of the control lever 78, regardless of variations in the compressor pressure or air induction pressure. That is to say, for each position of the lever 78 there will be a preselected rate of fuel supply which is properly proportioned to the weight flow of air to the combustion engine, irrespective of any variations which may occur in the pressure of the air fed to the combustion system. This means that, for a given air fiow to the powerplant, the pilot or operator may select the rate of fuel supply by positioning the lever 78. However such arrangement, in which the selection of the fuel-air ratio is left entirely to the choice of the pilot is not quite suitable in connection with aircraft propulsion powerplants. Accordingly, one of the objects of the invention is to provide, in combination with the previously disclosed arrangements, means responsive to one or more engine operating conditions, such as the air pressure or density in the induction system, whereby the action of the manual control lever 78 may be over-ridden and the fuel-air ratio automatically controlled under predetermined conditions as a function of certain operating parameters.

To that end the lever 79 of FIGURE 1 may be replaced by a lever 137, shown in FIGURE 2, provided with an upper arm which is the same and serves the same purpose as the upper arm of lever 79'. The lower arm of lever 137 is connected with the control lever 78 by means of a lost-motion device such as a pin 138 engaging an elongated slot 138 formed at one end of a rod the opposite end of which is pivoted to lever 78. A tension spring 139 exerts a biasing action on the lever 137 tending to rotate the same clockwise. The lever 137 is further provided with a third arm which is adapted to be engaged and actuated by a cam 146 mounted on a pivot or shaft 145. The cam 146 may be rotated by means of a lever 143 which is actuated by a device comprising a bellows 141, evacuated totally or in part and enclosed in a housing 140 communicating with the engine air induction system on the discharge side of the compressor 61. The bellows 141 operates a pilot valve 142 of a servo mechanism having a power piston whose stem is connected with the cam lever 143, the arrangement being such that an increase in compressor pressure raises the pilot valve 142 and causes counter-clockwise rotation of lever 143 until the increasing load of the tension spring 144 restores the balance of the pilot valve 142 in its neutral position. Hence the angular setting of the cam is determined in accordance with air induction or compressor pressure, and the cam 146 in turn determines for each value of induction air pressure a corresponding predetermined or minimum value of the fuel-air ratio. In the preferred embodiment the configuration of the cam is such that in the cruising range such minimum value corresponds substantially to the best economy mixture, while under higher power output the minimum fuel-air ratio obtainable will be higher than that corresponding to best economy mixture. Due to the lost motion connection provided by the elongated slot 138 and spring 139', the cam is adapted to over-ride the manual lever 78 and take over control of the lever 137 under predetermined pressure conditions of the powerplant. The particular point at which the actual control of lever 137 shifts from manual to automatic evidently depends upon the setting of the pilots lever 78.

It will be appreciated from the foregoing that in the preferred embodiment disclosed herein the variable control oil pressure device is constantly operating upon the fuel control valve 72 in cooperation with variable-ratio lever means 74 and, in the case of FIGURE 2, with the lost-motion connection 137438446. The foregoing embodiments of the invention have been described for purpose of illustration and not as a limitation of the scope of the invention. It is to be expressly understood that various modifications may be made to satisfy dilferent requirements, as will be obvious to those skilled in the art, and that changes, substitutions, additions and omissions may be made in the design, construction, arrangement and manner of operation of the parts and components without departing from the limits or scope of the invention as defined in the following claims.

Where the claims are directed to less than all of the elements of the complete system disclosed, they are intended to cover possible uses of the recited elements in installations which do not include the non-recited elements.

I claim:

1. In means for automatically controlling the supply of liquid fuel to a prime mover in response to variations in liquid fuel pressure and blower-air pressure, the combination with a movable part to be actuated by blowerair pressure of a body having therein a chamber, a fluid pressure responsive member dividing the chamber in two compartments and operatively connected to said movable part, means for admitting air at blower-air pressure into one of said compartments, a capsule located in the other compartment and operatively connected to said pressure responsive member to oppose the action of the air at blower pressure thereon, said capsule dividing the second mentioned compartment in a first portion which is evacuated and a second portion which is vented to sub stantially atmospheric pressure, said capsule having an eflective diameter less than that of the pressure responsive member whereby the force exerted on said member is in part dependent on the absolute pressure of the blower air and in part on the difference between the pressure of blower air and atmospheric pressure, whereby the fuelair ratio supplied to the prime mover may be maintained at desired values.

2. Means according to claim 1, in which the part to be actuated comprises a valve for controlling a liquid operated servo-mechanism, and further comprising valve means for controlling the supply of fuel actuated by said servo-mechanism.

3. A pressure operated valve for automatically con trolling the supply of liquid fuel to a prime mover supplied with air froma blower comprising, in combination, a valve-actuating movable part, means responsive to liquid fuel pressure for actuating said part, a chamber, a fluid pressure responsive member operatively connected to said movable part and dividing said chamber into two compartments, means for afiording a connection for air at blower air pressure to one of said compartments, a capsule located in the other of said compartments operatively connected to said pressure responsive member to oppose the action of the air at blower pressure thereon and defining in said second mentioned compartment an evacuated portion and a portion which is maintained at substantially atmospheric pressure, said capsule having an efiective diameter less than that of the pressure responsive member whereby the force exerted on said memher will be in part dependent on the absolute pressure of blower air and in part on the diflerence between the pressure of blower air and blower inlet or atmospheric pressure.

4. In a hydro-mechanical liquid fuel control for a thermal powerplant provided with an air intake system with a compressor therein, a hydraulic cylinder with a slidable piston defining a pressure chamber, means for supplying a control fluid under pressure to said chamber, a first mechanism for varying the fuel supply rate in accordance with the pressure in said chamber, first means including a pilot valve for controlling the admission of high pressure control fluid to said chamber or the drainage of said fluid therefrom, a follow-up lever connecting the piston with the pilot valve, a variable ratio lever mechanism operatively connected to the follow-up lever, a servo motor connected to said lever mechanism and operable to vary the effective lever ratio thereof, means responsive to compressor discharge pressure for controlling said servo motor, and additional control means operatively connected with said follow-up lever for varying the operative setting thereof to regulate the engine fuelair ratio.

5. In a liquid fuel controller for an engine provided with an air induction system with a compressor therein, a hydraulic cylinder with a slidable piston defining a pressure chamber, means for supplying a control fluid under pressure to said chamber, a first mechanism for varying the fuel supply rate in accordance with changes in pressure in said chamber, a pilot valve for controlling the pressure in said chamber, follow-up means connecting the piston with the pilot valve, a variable ratio lever mechanism for varying the operative setting of said follow-up means, a servo motor connected to said lever mechanism and operable to vary the effective lever ratio thereof, means responsive to compressor discharge pressure for controlling said servo motor, and manually adjustable control means operatively connected with said follow-up lever for altering the operative setting thereof to 'vary the engine fuel-air ratio.

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